I use the stock bolts on my Syncros with the Rhein rims. As to
tightening them...First, the center hub is a pretty tight fit. If you
have rust on your hub (front) or drum (rear) it might be more difficult
to get the wheels on all the way. Cleaning off any loose rust with a
steel wire brush should help a little.

For torque, I use the tried and true of just a bit more than I can move
by hand with the stock tire iron. I step on the end (not my full
weight). This is probably somewhere around 100-150 foot pounds. On my
Syncro I'm definitely getting more than 3 or 4 turns (threads) on the
nuts.